The goal of the proposed studies is to investigate the link between posture and action in the acquisition of physical knowledge. Evidence from looking paradigms suggests that between 6 and 7 months infants begin to elaborate their conceptual knowledge about certain physical phenomena. Research on reaching has shown that the onset of postural abilities such as self-sitting (at approximately 6 months of age) expands infants' functional actions allowing access to new sources of information. A goal of the proposed research is to determine whether the onset of self-sitting is linked to the elaboration of conceptual knowledge. The studies will investigate whether the level of infant's postural ability (nonsitter, near-sitter, and sitter) is predictive of their behavior in a looking time experiment measuring conceptual relaxation. In addition, we will test whether there is a link between specific object manipulations and attaining elaborated conceptual knowledge. Finally, we will do a longitudinal study on whether infants can be taught to elaborate their concepts about physical events. The broad ranging objectives of this research have implications for gaining a better understanding how knowledge can be revealed in different experimental paradigms. The research bears on the issue of causal mechanisms in acquisition of physical knowledge and not treating age as an independent variable. There are also health related applications of this word For example, a better understanding of posture and action could lead to new therapies for sensorimotor handicaps. This research also bears on current issues in Down's syndrome research. It has been reported that infants with Down's syndrome often lack the urge to explore which could support the possible conclusion that exploratory activities have important cognitive consequences.